1. Field of the Invention
The present invention relates to a sealing device for achieving the lifelong lubrication of the moving parts of the various joints in a crawler track for earthmoving vehicles and the like, and for ensuring that the life of said device is comparable to that of the other components of the crawler track itself.
2. Discussion of the Background
As is known, the life of the crawler tracks of an earthmoving machine, both for civil or military use, is in practice determined by the degree of wear of the pins and/or the bushes which make up said crawler track.
When this wear has reached values which are no longer acceptable, it is necessary to perform an overhaul which requires the replacement of the worn parts, this operation unfortunately involving the disassembly of the entire crawler track or of every joint or every sealing device since all the joints (without exception) must be restored to their original dimensions. In view of the weight and the dimensions of the two crawler tracks of each machine and the specific equipment necessary for disassembly (such as, for example, at least one press of a suitable type), the operation may be performed in practice only in specialized workshops to where the machine or at least the two crawler tracks must be taken. In order to illustrate more fully the complexity of said operation, it should be considered that, after the cost of the fuel, depreciation of the crawler tracks, adding together the costs for maintenance and periodic replacement thereof, represents the largest item of expenditure in the running costs.
It goes without saying that the sealing devices, since they are components which are intended to prevent the penetration of abrasive foreign bodies into the joints and, if necessary, ensure that lubricant remains inside the latter, are of fundamental importance for the life of the crawler track. In practice, the penetration of foreign bodies into a joint results in wear of the surfaces in relative motion, including those of the sealing device. The effect of this is that the sealing device is increasingly less able to prevent the leakage of lubricant from the joint and the penetration of further abrasive foreign bodies between the surfaces in relative motion. This explains the reason why, in most cases, the wear, once it has started, subsequently develops in a relatively fast and increasingly rapid manner. In an attempt to find a solution to the abovementioned technical problem, the known art comprises various sealing devices, including also that described in Italian patent No. 1,230,329 filed on Jul. 11, 1989, compared to which the sealing device according to the invention may be regarded as a step forward. In order to facilitate understanding of the invention, reference numbers consistent with those in the abovementioned Italian patent have therefore been used in the description which follows.